Braking mechanism



Patented Sept. 24, 1940 UNITED STATES PATENT OFFICE 2,215,909 BRAKING MECHANISM William C. McWhirter and Edwin G. Little,

Wilkinsburg, Pa

assignors to The Union ber 19, 1938, Serial No.

10 Claims.

Our invention relates to braking mechanism, and more particularly to an electromagnetic brake for motor driven apparatus such, for example, as the apparatus utilized for operating railroad track 5 switches. 'In the operation of apparatus driven by electric motors, and particularly in the operation of railway switch operating apparatus it is desirable to-prev'ent operation of the apparatus except '1 when authorized power is applied, orwhen the apparatus is to be operated manually. One object of our invention is to provide an electromagnetic brake for accomplishing this result which brake maybe located within the motor housing, and

"f which is normally biased to a braking condition but which will become automatically released when'power is applied to the motor, or may be released b'ymanual means.

Other objects, purposes and characteristic feag9 tures of our inventionwill appear as the description proceeds.

The present application is a division of our copehding application for Letters Patent of the United States, Serial No. 148,706, filed on June 17,;

' 1937, which has become Patent No. 2,183,164, Dec.

1-2; 1939, for Railway switch operating apparatus.

a We shall describe one form of braking mechanism; embodying our invention, and shall then point out the novel features thereof in claims.

' in the accompanying drawing, Fig. 1 is a fragmentary sectional view of an electric motor which is provided with brake mechanism embodying our invention. Fig. .2 is a sectional View taken on the line 11-11 of Fig.- 1. Fig. 3 is a top plan view with cover removed of the brake mechanism shown in Fig. 2. p r Similar reference characters refer to similar parts in' all'three views. I

Referring to the drawing, we have here shown .4 a magnetic brake E embodying our invention applied to a direct current motor B of the usual and well-known.typecomprising an armature I30 and field coils I3I disposed in an enclosing casing I32, one end of which is provided with a removable cover-I33 through which convenient access to thecommutator and brushes, as well as to the magnetic brake E, may be had. The magnetic brake E comprises a brake disk I51 secured to a die casting I58 which is mounted 5 for longitudinal sliding movement on the armature shaft 65, but which is constrained to rotate with the armature shaft by means of a feather key I59. One side of the brake disk I51 cooperates with a brake lining I60 secured to a stationary brake shoe I'6I, and the other side-of this brake disk cooperates with a brake lining I62 secured to a movable brake shoe I63. The stationary brake shoe I6I is formed with an externally screw threaded hub I64, which hub is adjustably screwed into the inner end of the bearing 5 opening I65 in theen'd wall of the motor casing I 32. After the stationary brake shoe has once been adjusted to the desired position, it is subsequently maintained in this position by means of a locking screw Hi6 which is screwed through a threaded hole formed in the end wall of the motor casing, and which projectsat its inner ends to one of a plurality of holes I61 provided in the outer face of the stationary brake shoe I6| in a position to receive the screw. The movable brake shoe I 63 is provided with a hub I68 which is slidably mounted on a tubular support I69 formed ona supporting bracket I49 in concentric relation to the shaft 65. The supporting bracket I49 is secured to the opposite sides of the casing i 32 of motor B by means of top bolts I54, as shown in Figs. 2 and 3. Surrounding the hub I68 and the tubular support I 69 between the movable brake shoe and the support'is a compressed coil spring I18 which constantly biases the movable brake shoe and the brake disk I51 toward the stationary brake shoe to braking positions in which the two brake linings I 60 and I62 frictionally engage the brake disk I51. It will be apparent that when thenbr'ake linings are engaging the brake disk, rotation of the motor armature willbe resisted. The magnetic brake E also comprises an operating yoke I1! which is pivotally supported adjacent its upperend on a rod I12 mounted in spaced lugs I13 providedon the bracket-I49, and the arms I1Ia. and I1Ib of which extend downwar'dly past the opposite sides of the movable brake shoe I 63 and are'operatively connected intermediate their ends with the brake shoe by means of recesses I1Ic which are formed in the arms IIIa, and I1Ib, and-which cooperate with diametrically opposite laterally projecting lugs I15 provided on the brake shoe at its outer edge. Secured to the lower ends of the arms Illa and I1Ib are armatures I16 and I11, respectively, which cooperate with magnets FI and. F2 located in the bottom of the motor casing. As will be seen from an inspection of Fig. 2, the magnets FI and F2 are of the ironclad type, and each com-' prises a suitable cup-shaped shell I18 formed integrally with the motor casing, a central core member I19 securedat one end to the shell, and a winding I which surrounds the associated core member within the associated shell.

A tension spring I8I is hooked at one end onto a lug I82 provided on the end wall of the motor casing H30, and the other end of this spring is secured to a bolt I83 which extends with clearance through a hole I'I id provided in a channelshaped ofiset portion I'IIe formed on the upper end of the operating yoke I'II. An adjusting nut I85 is screwed onto the outer end of the bolt I83 and formed on the inner end of this nut is a wedge-shaped surface I86 which cooperates with a notch I'IIf provided in the adjacent space of the offset portion, whereby when the nut I85 has been rotated to any position in which the wedge-shaped surface I86 aligns with the notch, the tension of the spring IBl will act to hold the wedge-shaped surface in the notch, and will thus prevent the nut from becoming unscrewed and destroying the adjustment. The spring ItI exerts a force on the operating yoke IlI which rotates the yoke in a clockwise direction, as viewed in Fig. 1, about the rod IIP. to the position in which the recess I"II c on the arms llIa and I'Iib receives the lug I15 on the movable brake shoe M33, and it will be seen, therefore, that the spring I8I serves to take up any clearance surrounding pin H2 in such a way that the air gap between the armatures I16 and Ill and the associated magnets Fl and F2 is held to the minimum. It will further be seen that due to the connection between the yoke Ill and the movable brake shoe I63, the force due to the spring I8I opposes the force which is exerted on the movable brake shoe by the spring ill], and it follows, thereiore,,that by adjusting the nut I85 to different positions, the resultant force which is exerted on the movable brake disk 515, and hence the braking force exerted by the brake may be quickly and conveniently varied to any desired value within the limits of the apparatus.

The windings IBIi of the two magnets FI and F2 are adapted to be connected in series in the operating circuit for the motor B in such manner that the motor current will flow in these windings, and it will be apparent that whenever the motor is deenergized, the spring I10 will actuate the brake to its braking position, and will thus cause the brake to opposerotation of the motor armature. When, however, the motor becomes energized,'the magnets FI and F2 will attract the armatures I16 and Ill, and will thus rotate the operatin yoke Ill in a clockwise direction as viewed in Fig. 1. This rotation will act through the recesses I'IIc and lugs M5 to slide the movable brake shoe I63 toward the left, in opposition to the bias of the spring ill], to a position in which the pressure of the brake linings against the brake disk I151 is removed, thereby releasing the brake, and hence permitting the motor armature to rotate without opposition from the brake It will be readily understood that when the armatures I16 and Ill are moved to their attracted positions, the reluctances of the flux paths for the fluxes set up by the energized windings will be considerably reduced due to the decreased air gaps between the armatures and the magnets, and that, as a result, the current required to hold the armatures H6 and Ill in their attracted positions will be considerably less than that required to move them to their attracted positions. It is desirable that the magnets should not become energized at current values below that flowing in the motor circuit under starting conditions, in order to prevent improper operation of-the motor due to stray currents which may be supplied to the motor, and it follows that by properly adjusting the air gaps which exist between the armatures and the magnets when the armatures occupy their deenergized positions, the characteristics of the brake may be so adjusted that it will be necessary for a current to flow in the windings I corresponding to the current which flows in the motor under normal starting conditions in order to release the brake, but that the brake will be maintained in its released position by a reduced current which is equal to the normal operating current for the m0- tor. The necessary adjustment to accomplish this required result may be made by unscrewing the locking screw- Hi6 and rotating the stationary brake shoe I6I in one direction or the other. This rotation will move the stationary shoe in an axial direction toward or away from the bracket I49, which movement, in turn, will cause a corresponding movement of the movable brake shoe I33, thereby causing the operating yoke ill to rotate to a new position'in which the armatures I16 and Ill are closer to, or farther away from, the magnets-as the case may be. After the necessary adjustment has been made,

the stationary brake shoe may again be locked against rotation by means of the locking screw The magnetic brake further comprises means for at times manually releasing the brake. As here shown, these means comprise a push rod 215 (Fig. 3) which is slidably mounted in one end of the casing i32 of motor B, and which cooperates at its inner end with a boss I'I Io provided on the depending arm I'I lb of the clutch operating yoke Ill in such manner that by moving the rod 2Y5 inwardly the yoke I'II can be rotated in a clockwise direction, as viewed in Fig. 1, in opposition to the bias of the spring I'IO to the same position to which this yoke is moved when the electromagnets FI and F2 become energized. The outer end of the push rod I15 is pivotally attached to one end of a bell crank lever 216 which is pivotally secured to; the motor casing,

" whereby suitable means for manually operating the push rod may be operatively connected there- Ting our invention is that adjustments which may be necessary due to wear of the brakeplining, and to adapt the brake to different operating positions may be quickly .and conveniently made.

Anotheradvantage of braking mechanism embodying our invention is that the operation of the brake when the motor becomes energized is positive, thus insuring that the brake will not drag. Although we have herein shown and described only one form of braking mechanism embodying our invention, it is understood that various changes and modifications may be made therein within the scope of the appended claims without departing from the spirit and sco'pe'oi our invention. 7

Having thus described our invention, what We claim is:

1. In combination, an electric motor, a brake disk slidablymounted on the armature shaft and rotatable therewith, a brakeshoe adjustably secured to the motor housing on one side of said "('5 disk, a second brake shoe disposed-on theother 'ferent positions of said stationary brake shoe side of said disk for sliding movementtoward and away from. said first -disk,'adjustable spring means for biasing said second brake shoe-toward said fixed brake shoe to cause said brake shoes to frictionally engage said brake disk, a yoke pivotally mounted at one end and pivotally'connected intermediate its ends with said brake shoe, 'a pair of armatures secured to the other end of said yoke, and two electromagnets cooperating with said two armatures, respectively, and effective when energized for moving said yoke to move said slidable brake shoe away from said fixed brake shoe in opposition to the bias of said spring means. V i 1 2. In combination, an electric motor, a brake disk slidably mounted on the armature shaft'and rotatable therewith, a brake shoe adjustably secured to the motor housing on one side of said disk, a second brake shoe disposed on the other side of said diskfor sliding movement toward and away from said first disk, adjustablespring means for biasing said second brake shoe toward said fixed brake shoe to cause said brake shoes to frictionally engage said brake disk, a yoke pivotally mounted at one end and pivotally connected intermediate its ends with said brake shoe, a pair of armatures secured to-the other end of said yoke, and two electromagnets cooperating with said two armatures, respectively, and effective when energized for moving said yoke to move said slidable brake shoe away from said fixed brake shoe in opposition to the bias of said spring means, each said electromagnet being provided with a shell which is cast integrally-with the motor frame.

3..In combination, an electric motor, a brake disk slidably mounted on the armature shaft and rotatable therewith, a stationary brake shoe disposed on one side of said brake disk and provided with a hub which is adjustably screwed into the inner end of the one armature bearing opening in the motor frame, a locking screw screwed through the motor frame and projecting at its inner end into a selected one of a plurality of holes provided in the outer face of said stationary brake shoe in positions to receive said screw in different positions of said stationary brake shoe to lock said stationary brake shoe in an adjusted position, a second brake shoe disposed on the other side of said disk for sliding movement toward and away from said disk, spring means for forcing said second brake shoe toward said stationary brake shoe to cause said brake shoes to frictionally engage said brake disk, a yoke pivotally mounted at one end and pivotally c'onnected intermediate its ends with said second rake shoe and effective when rotated in one direction for moving said second brake shoe away from said fixed shoe in opposition to the bias. of said spring means, and electromagnetic means cooperating with the other end of said yoke to actuate said yoke in a manner to move said second brake shoe away from said fixed shoe.

4. In combination, an electric motor, a brake disk slidably mounted on the armature shaft and rotatable therewith, a stationary brake shoe disposed on one side of said brake disk and provided with a hub which is adjustably screwed into the inner end of the one bearing opening in the motor frame, a locking screw screwed through themotor frame and projecting at its inner end into a selected one of a plurality of holes provided in the outer face of said stationary brake shoe in positions to receive said screw in difto lock said stationary brake shoe in an adjusted position, a second brake shoe disposed on the other side of said disk for sliding movement toward and away from said first disk, adjustable spring means for biasing said second brake shoe toward said stationary brake shoe to cause said brake shoes. to frictionally engage said brake disk, a yoke pivotally mounted at one end and pivotally connected intermediate its ends with said second brake shoe, a pair of armatures secured to-theother endof said yoke, and two electro- 'magnets cooperating with said two armatures, re-

spectively, and efiective when energized for moving said yoke tomove said second brake shoe away from said fixed brake shoe in opposition to-the'bias ofsaid spring means.

' 5; In combination, an electric-motor, a brake disk slidably mounted on the armature shaft and rotatable therewith, a fixed brake shoe on one side'of said disk, a bracket secured to the motor frame and providedwith a tubular support which surrounds the armature shaft on the side of said brake disk opposite to said fixed brake shoe, a

second brake shoe provided with a hub which is slidably mounted on said tubular support, a com- "pressed coil spring surrounding the hub of said second brake shoe and said tubular support be tween'said bracket and said second brake shoe and effective for forcing said second brake shoe toward said fixed brake shoe to cause said brake said second brake shoe away from said fixed shoe. 7

6. In combination, an electric motor, a brake disk slidably mounted on the armature shaft and rotatable therewith, a fixed brake shoe disposed on one side of said brake disk and provided with a hub which is adjustably screwed into the inner end of the one bearing opening in the motor frame, a locking screw screwed through the motor frame and projecting at its inner end into a selectedone of a plurality of holes provided in the outer face of said fixed brake shoe in positions to receive said screw in different positions of said fixed brake shoe to lock said fixed brake shoe in an adjusted position, a bracket secured to the motor frame and provided with a tubular support which surrounds the armature shaft on the side of said brake disk opposite to said fixed brake shoe, a second brake shoe' provided with a hub which is slidably mounted on said tubular support, a compressed I coil spring surrounding the hub of said second brake shoe and said tubular support between said bracket and said second brake shoe and effective for forcing said second brake shoe toward said fixed brake shoe to cause said brake shoes to frictionally engage said brake disk, a yoke pivotally mounted at one end and pivotally connected intermediate its ends with said second brake shoe and effective when rotated in one direction for moving said second brake shoe-away from said fixed shoe in opposition to the bias of said spring means, and electromagnetic means cooperating with the other end of said yoke to actuate said yoke in a manner to move said second brake shoe away from said fixed shoe.

'7. In combination, an electric motor, a brake disk slidably mounted on the armature shaft and rotatable therewith, a fixed brake shoe on one side of said disk, a second brake shoe disposed on the other side of said disk for sliding movement toward and away from said disk, a. first spring for forcing said second brake shoe toward said fixed brake shoe to cause said brake shoes to frictionally engage said brake disk, a yoke pivotally mounted at one end and pivotally connected intermediate its endswith said second brake shoe and effective when rotated in one direction for moving said second brake shoe away from said fixed shoe in opposition to the bias of said spring means, electromagnetic means cooperating with the other end of said yoke to actuate said yoke in a manner to move said second brake shoe away from said fixed shoe, and a second spring connected with said yoke in a direction to oppose said first spring, and means for varying the force exerted on said yoke by said second spring to vary the force with which said slidable brake shoe is biased toward said fixed brake shoe.

8. In combination, an electric motor, a brake disk slidably mounted on the armature shaft and rotatable therewith, a fixed brake shoe disposed on one side of said brake disk, a bracket secured to the motor frame and provided with a tubular support which surrounds the armature shaft with clearance on the side of said brake disk opposite to said fixed brake shoe, a second brake shoe having a hub slidably mounted on said tubular support for movement toward and away from said brake disk, a compressed coil spring disposed between said bracket and said second brake shoe and effective for biasing said second brake shoe toward said fixed brake shoe to cause said two brake shoes to frictionally engage said brake disk, a yoke pivotally secured to said bracket and pivotally connected with said second brake shoe, a tension spring secured at one end to the motor casing and at the other end to said yoke by means whereby the tension of said spring can be varied and acting through said yoke to exert on said second brake shoe a force which opposes and which is less than that due to said compressed coil spring, and electromagnetic means for actuating said yoke in a direction to move it away from said fixed brake shoe.

9. In combination, an electric motor, two electromagnetseach provided with a shell which is cast integrally Withthe motor frame, and braking means for the armature shaft of said motor controlled by said electromagnets,

10. In combination, an electric motor, a brake disk slidably mounted on the armature shaft of said motor and constrained to rotate therewith, a fixed and a movable brake shoe cooperating with said brake disk on opposite sides thereof, means for biasing said movable shoe toward said fixed shoe to cause said shoes to frictionally engage said brake disk, two electromagnets each provided with a shell which is cast integrally with the motor frame, and means controlled by said electromagnetsfor at times moving said movable brake shoe away from said fixed brake shoe to release the brake formed by said two shoes and said disk.

' WILLIAM C. MCWHIR'IER.

EDWIN G. LITTLE. 

